Triboelectric generator

ABSTRACT

A triboelectric generator includes a first electrode and a second electrode spaced apart from each other, a first charging part on the first electrode, a second charging part on the second electrode, and a grounding unit. The first charging part and the second charging part may be configured to contact each other through a sliding motion. The grounding unit may be configured to intermittently connect a charge reservoir to the second charging part. The grounding unit may be configured to vary the electric potential of the second charging part so as to amplify current flowing between electrodes of the triboelectric generator.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/589,091, filed May 8, 2017, which claims the benefit of Korean PatentApplication Nos. 10-2016-0057217, filed on May 10, 2016, and10-2016-0057218, filed on May 10, 2016, in the Korean IntellectualProperty Office, the entire disclosures of which are incorporated hereinby reference.

BACKGROUND 1. Field

The present disclosure relates to triboelectric generators, and moreparticularly, to triboelectric generators having grounding structures.

2. Description of Related Art

Recently, there is increasing interest in energy harvesting techniques.Energy harvesting devices capable of converting energy of surroundingssuch as mechanical energy of wind, vibration, or human body motion intoelectric energy and extracting the electric energy may be considered asnew eco-friendly energy generating devices.

Triboelectric generators are energy harvesting devices configured togenerate electric energy using a charge transfer phenomenon occurringwhen two charging parts rub together. Triboelectric generators have ahigh degree of energy conversion efficiency, and thus if triboelectricgenerators are used, a high degree of output may be obtained even by asmall amount of force. In addition, triboelectric generators do not havetime or spatial limitations compared to energy harvesting devices usingheat or sunlight, and it is possible to continuously generate electricenergy using triboelectric generators unlike the case of usingpiezoelectric energy harvesting devices configured to generate electricenergy by deforming a piezoelectric material.

SUMMARY

Some example embodiments provide triboelectric generators includinggrounding structures.

Additional aspects will be set forth in part in the description whichfollows and, in part, will be apparent from the description, or may belearned by practice of the presented embodiments.

According to some example embodiments, a triboelectric generatorincludes a first electrode and a second electrode spaced apart from eachother, a first charging part and a second charging part, and a groundingunit. The first charging part is on the first electrode. The firstcharging part is configured to be charged a first polarity due tocontact with the second charging part. The second charging part isconfigured to slide on a surface of the first charging part. The secondcharging part is configured to charge a second polarity that is oppositethe first polarity through contact with the first charging part. Thegrounding unit is configured to intermittently connect the secondcharging part to a charge reservoir according to movement of the secondcharging part.

In some example embodiments, the second charging part may be configuredto slide on a surface of the second electrode as well as on the surfaceof the first charging part.

In some example embodiments, the first electrode and the secondelectrode may be spaced apart from each other in a direction in whichthe second charging part is configured to slide.

In some example embodiments, the first charging part may be on an uppersurface of the first electrode, and the upper surface of the firstelectrode may face the second charging part.

In some example embodiments, the grounding unit may be between the firstelectrode and the second electrode, and the second charging part may beconfigured to slide on an upper surface of the grounding unit.

In some example embodiments, a distance between the first charging partand the grounding unit may be less than a width of the second chargingpart, and a distance between the second electrode and the grounding unitmay be less than the width of the second charging part.

In some example embodiments, the first electrode, the grounding unit,and the second electrode may be on a first substrate.

In some example embodiments, the first substrate has a cylindrical shapeor a circular post shape.

In some example embodiments, the triboelectric generator may furtherinclude a second substrate having a cylindrical shape surrounding thefirst substrate, and the second charging part may be on an inner surfaceof the second substrate.

In some example embodiments, the first substrate may have a circularplate shape, and the first electrode, the grounding unit, and the secondelectrode may be arranged on the first substrate in radial directions.

In some example embodiments, the triboelectric generator may furtherinclude a second substrate having a circular plate shape facing thefirst substrate, and the second charging part may be on the secondsubstrate.

In some example embodiments, the second charging part may be configuredto slide on the first charging part while rotating relative to the firstcharging part, and the first electrode and the second electrode may bespaced apart from each other in a direction perpendicular to a directionin which the second charging part is configured to slide.

In some example embodiments, the first charging part may be on a lowersurface of the first electrode facing the second charging part.

In some example embodiments, the grounding unit may be electricallyconnected to the charge reservoir, and the grounding unit may include aconductive post configured to intermittently contact the second chargingpart when the second charging part rotates.

In some example embodiments, the grounding unit may include a conductivemember and an insulative member alternately arranged in a direction inwhich the second charging part rotates, and the conductive member may beelectrically connected to the charge reservoir and configured tointermittently contact the second charging part.

In some example embodiments, the first charging part, the secondcharging part, and the second electrode may have a fan shape.

In some example embodiments, the triboelectric generator may furtherinclude: a first magnetic part below the first electrode; and a secondmagnetic part above the second electrode.

In some example embodiments, the second electrode may be configured tobe moved relative to the second charging part by magnetic force betweenthe first magnetic part and the second magnetic part, andmutually-facing surfaces of the first magnetic part and the secondmagnetic part may have a same polarity.

In some example embodiments, the first magnetic part may be interlockedwith the first electrode and the first charging part.

In some example embodiments, a lower surface of the second charging partmay be configured to contact an upper surface of the first charging partwhile the second charging part rotates relative to the first chargingpart.

In some example embodiments, the first electrode, the first chargingpart, the grounding unit, and the first magnetic part may be configuredto interlock with each other and to rotate relative to the secondcharging part.

In some example embodiments, the second electrode and the secondcharging part may be configured to contact each other or to separatefrom each other depending on a distance between the first magnetic partand the second magnetic part.

In some example embodiments, the second electrode interlocked with thesecond magnetic part may be configured to contact an upper surface ofthe second charging part when the first charging part and the secondcharging part contact each other.

In some example embodiments, the first charging part may be configuredto be charged with a negative charge, and the second charging part maybe configured to be charged with a positive charge.

In some example embodiments, the first charging part may be charged witha positive charge, and the second charging part may be charged with anegative charge.

In some example embodiments, the charge reservoir may include a groundor a conductive member.

According to some example embodiments, a triboelectric generator mayinclude a first electrode, a first charging part on the first electrode,a second electrode spaced apart from the first electrode, a secondcharging part configured to contact a surface of the first charging partthrough sliding motion, and a grounding unit configured tointermittently connect the second charging part to a charge reservoiraccording to movement of the second charging part. The first chargingpart may have a first charging rating. The first charging part mayinclude a first material. The second charging part may have a secondcharging rating that is different than the first charging rating. Thesecond charging part may include an electrically conductive materialthat is different than the first material.

In some example embodiments, the grounding unit may be between the firstelectrode and the second electrode, and the second charging part may beconfigured to slide on an upper surface of the grounding unit.

In some example embodiments, the first charging part may include atleast one of an organic polymer, an inorganic polymer, an organicallymodified ceramic. The second charging part may include a metallicmaterial.

In some example embodiments, the second charging part may be configuredto slide on the first charging part while rotating relative to the firstcharging part, and the first electrode and the second electrode may bespaced apart from each other in a direction perpendicular to a directionin which the second charging part is configured to slide.

In some example embodiments, a distance between the first charging partand the grounding unit may be less than a width of the second chargingpart, and a distance between the second electrode and the grounding unitmay be less than the width of the second charging part.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects will become apparent and more readilyappreciated from the following description of non-limiting embodiments,taken in conjunction with the accompanying drawings in which:

FIG. 1 is a perspective view illustrating a triboelectric generatoraccording to some example embodiments;

FIG. 2 is a cross-sectional view illustrating the triboelectricgenerator shown in FIG. 1;

FIG. 3 is a view illustrating a modification of the triboelectricgenerator shown in FIG. 2;

FIG. 4 is a view illustrating a modification of the triboelectricgenerator shown in FIG. 2;

FIG. 5 is a view illustrating a sliding motion of a second charging partrelative to a first charging part;

FIG. 6 is a view illustrating a state in which the second charging partmeets a grounding unit as a result of a sliding motion;

FIG. 7 is a view illustrating a state in which the second charging partis further moved relative to a substrate through a sliding motion;

FIG. 8 is a view illustrating a state in which the second charging partmeets a second electrode as a result of a sliding motion;

FIG. 9 is a view illustrating a state in which the second charging partis further moved relative to the substrate through a sliding motion;

FIG. 10 is a view illustrating a state in which the second charging partis separated from the second electrode as a result of a sliding motion;

FIG. 11 is a view illustrating a state in which the second charging partapproaches the first charging part;

FIG. 12 is a view illustrating a state in which the second charging partcontacts the first charging part through a sliding motion;

FIG. 13 is a view illustrating a state in which the second charging partmeets the grounding unit as a result of a sliding motion;

FIG. 14 is a view illustrating a state in which the electric potentialof the second charging part varies as a result of a flow of electronsshown in FIG. 13;

FIG. 15 is a view illustrating a state in which the second charging partis further moved relative to the substrate through a sliding motion;

FIG. 16 is a view illustrating a state in which the second charging partcontacts the second electrode as a result of a sliding motion;

FIG. 17 is a view illustrating a state in which the second charging partis separated from the second electrode as a result of a sliding motionin the state shown in FIG. 16;

FIG. 18 is a perspective view illustrating a triboelectric generatorhaving a different shape according to some example embodiments;

FIG. 19 is a perspective view illustrating a triboelectric generatorhaving a different shape according to some example embodiments;

FIG. 20 is a perspective view illustrating a triboelectric generatorhaving a different shape according to some example embodiments.

FIG. 21 is a perspective view illustrating a triboelectric generatorhaving a different shape according to some example embodiments;

FIG. 22 is a perspective view illustrating a triboelectric generatorhaving a different shape according to some example embodiments;

FIG. 23 is illustrates a triboelectric generator having a differentshape according to some example embodiments;

FIG. 24 is a schematic cross-sectional view illustrating a triboelectricgenerator according to some example embodiments;

FIG. 25 is a view illustrating a state in which first and secondcharging parts are in contact with each other;

FIG. 26 is a view illustrating a state in which the second charging partcontacts a grounding unit;

FIG. 27 is a view illustrating a state in which the second charging partcontacts a second electrode;

FIGS. 28 and 29 are views illustrating the second charging partseparating from the second electrode and the first charging part;

FIG. 30 is a view illustrating a modification of the triboelectricgenerator shown in FIG. 23;

FIG. 31 is a cross-sectional view illustrating a triboelectric generatoraccording to some example embodiments;

FIG. 32 is a view illustrating a modification of the triboelectricgenerator shown in FIG. 31;

FIG. 33 is a view illustrating a state in which first and secondcharging parts shown in FIG. 31 are in contact with each other;

FIG. 34 is a view illustrating a state in which the second charging partis moved relative to the first charging part through a sliding motion;

FIG. 35 is a view illustrating a state in which the second charging partcontacts a grounding unit through a sliding motion;

FIG. 36 is a view illustrating a state in which the second charging partapproaches again the first charging part after the cycle described withreference to FIGS. 31 to 34 is completed;

FIG. 37 is a view illustrating a state in which the second charging partcontacts the first charging part as a result of a sliding motion;

FIG. 38 is a view illustrating a state in which the second charging partis moved relative to the first charging part through a sliding motion;

FIG. 39 is a view illustrating a state in which the second charging partcontacts the grounding unit through a sliding motion;

FIG. 40 is a current-time graph of the triboelectric generator shown inFIGS. 1 to 17, illustrating current flowing between first and secondelectrodes, and current flowing in the grounding unit;

FIG. 41 is a graph for comparing an output current measured between thefirst and second electrodes of the triboelectric generator shown inFIGS. 1 to 17 with an output current measured between the first andsecond electrodes of the triboelectric generator after the groundingunit was removed from the triboelectric generator;

FIG. 42 is a graph for comparing a voltage measured between the firstand second electrodes of the triboelectric generator shown in FIGS. 1 to17 with a voltage measured between the first and second electrodes ofthe triboelectric generator after the grounding unit was removed fromthe triboelectric generator;

FIG. 43 is a perspective view illustrating a triboelectric generatoraccording to some example embodiments;

FIG. 44 is a side view illustrating the triboelectric generator shown inFIG. 43;

FIG. 45 is a top view illustrating the triboelectric generator shown inFIG. 43;

FIG. 46 is a view illustrating a state in which first and secondcharging parts contact each other as a result of a sliding motion;

FIG. 47 is a side view illustrating the triboelectric generator shown inFIG. 46;

FIG. 48 is a top view illustrating the triboelectric generator shown inFIG. 46;

FIG. 49 is a view illustrating a state in which the first charging partis further rotated relative to the second charging part;

FIG. 50 is a side view illustrating the triboelectric generator shown inFIG. 49;

FIG. 51 is a top view illustrating the triboelectric generator shown inFIG. 49;

FIG. 52 is a view illustrating a state in which the first charging partis further rotated relative to the second charging part;

FIG. 53 is a side view illustrating the triboelectric generator shown inFIG. 52;

FIG. 54 is a top view illustrating the triboelectric generator shown inFIG. 52;

FIG. 55 is a view illustrating a state in which the first charging partis further rotated relative to the second charging part;

FIG. 56 is a side view illustrating the triboelectric generator shown inFIG. 55;

FIG. 57 is a top view illustrating the triboelectric generator shown inFIG. 55;

FIG. 58 is a view illustrating a modification of the triboelectricgenerator shown in FIG. 44;

FIG. 59 is a view illustrating a modification of the triboelectricgenerator shown in FIG. 44;

FIG. 60 is a view illustrating a triboelectric system according to someexample embodiments; and

FIG. 61 is a view illustrating a triboelectric system according to someexample embodiments.

DETAILED DESCRIPTION

Reference will now be made in detail to some example embodimentsillustrated in the accompanying drawings, wherein like referencenumerals refer to like elements throughout. In this regard, the presentembodiments may have different forms and should not be construed asbeing limited to the descriptions set forth herein. Accordingly, theembodiments are merely described below, by referring to the figures, toexplain aspects. As used herein, the term “and/or” includes any and allcombinations of one or more of the associated listed items. Expressionssuch as “at least one of,” when preceding a list of elements, modify theentire list of elements and do not modify the individual elements of thelist.

The terms used in the present disclosure are general terms currentlywidely used in the art in consideration of functions regarding inventiveconcepts, but the terms may vary according to the intention of those ofordinary skill in the art, precedents, or new technology in the art.Also, some terms may be arbitrarily selected by the applicant, and inthis case, the meaning of the selected terms will be described in thedetailed description of the present disclosure. Thus, the terms usedherein should not be construed based on only the names of the terms butshould be construed based on the meaning of the terms together with thedescription throughout the present disclosure.

In the following descriptions of embodiments, when a portion or elementis referred to as being connected to another portion or element, theportion or element may be directly connected to the other portion orelement, or may be electrically connected to the other portion orelements with intervening portions or elements being therebetween. Itwill be further understood that the terms “comprises” and/or“comprising” used herein specify the presence of stated features orelements, but do not preclude the presence or addition of one or moreother features or elements. In the descriptions of the embodiments,terms such as unit or module are used to denote a unit having at leastone function or operation and implemented with hardware, software, or acombination of hardware and software.

In the following descriptions of the embodiments, expressions or termssuch as “constituted by,” “formed by,” “include,” “comprise,”“including,” and “comprising” should not be construed as alwaysincluding all specified elements, processes, or operations, but may beconstrued as not including some of the specified elements, processes, oroperations, or further including other elements, processes, oroperations.

In addition, although the terms “first” and “second” are used todescribe various elements, these elements should not be limited by theseterms. These terms are only used to distinguish one element from otherelements.

The following descriptions of the embodiments should not be construed aslimiting the scope of inventive concepts, and modifications or changesthat could be easily made from the embodiments by those of ordinaryskill in the art should be construed as being included in the scope ofinventive concepts. Hereinafter, example embodiments will be describedwith reference to the accompanying drawings.

FIG. 1 is a perspective view illustrating a triboelectric generatoraccording to some example embodiments. FIG. 2 is a cross-sectional viewillustrating the triboelectric generator shown in FIG. 1.

Referring to FIGS. 1 and 2, the triboelectric generator may include afirst electrode 122 and a second electrode 124 spaced apart from eachother, a first charging part 110 disposed on a surface 51 of the firstelectrode 122, a second charging part 140 slidable in a direction(x-axis direction) on a surface S2 of the first charging part 110 and asurface S3 of the second electrode 124, and a grounding unit 130configured to intermittently connect the second charging part 140 to acharge reservoir 133 according to the movement of the second chargingpart 140. The triboelectric generator may include a sliding mechanism toinduce a horizontal motion of the second charging part 140 relative tothe first charging part 110 or the second electrode 124 by an externallyapplied force and thus to bring adjacent surfaces into contact with eachother.

The second charging part 140 may rub on an upper surface of the firstcharging part 110 through a sliding motion. Here, the expression “thesecond charging part 140 slides” refers to that the second charging part140 moves relative to the first charging part 110, the grounding unit130, and the second electrode 124. Therefore, sliding of the secondcharging part 140 may occur as the second charging part 140 moves. Inaddition, sliding of the second charging part 140 may occur as the firstcharging part 110, the grounding unit 130, and the second electrode 124move relative to the second charging part 140. In addition, theexpression “the second charging part 140 slides in a direction” refersto that the second charging part 140 slides in a direction in which thefirst charging part 110, the grounding unit 130, and the secondelectrode 124 are arranged. Therefore, the movement of the secondcharging part 140 is not limited to straight movement.

The first charging part 110 may include a first material. The secondcharging part 140 may include a second material that is a differentmaterial than the first material. For example, the second charging part140 and the first charging part 110 may include materials havingdifferent charging ratings. Therefore, if a surface of the secondcharging part 140 is rubbed against the surface S2 of the first chargingpart 110, the surface S2 of the first charging part 110 and the surfaceof the second charging part 140 may be charged with differentpolarities. The types of charges of the first charging part 110 and thesecond charging part 140 are dependent on materials of the firstcharging part 110 and the second charging part 140, for example, may bedetermined by relative positions of the materials of the first chargingpart 110 and the second charging part 140 in a triboelectric series.

For example, the surface S2 of the first charging part 110 may becharged with a negative charge by friction with the second charging part140, and the surface of the second charging part 140 may be charged witha positive charge by friction with the first charging part 110. Thesecond charging part 140 may include a conductive material for easyelectric connection with the grounding unit 130. The conductive materialmay include a metallic material that is easily charged by friction, suchas aluminum (Al), copper (Cu), gold (Au), or steel. In addition, thefirst charging part 110 may include at least one ofpolytetrafluoroethylene (Teflon), fluorinated ethylene propylene (FEP),poly(methyl methacrylate) (PMMA), polyvinylidene fluoride (PVDF),polycarbonate (PC), polyvinyl chloride (PVC), polyimide (Kapton),polypropylene (PP), polyethylene (PE), and polystyrene (PS) that areeasily charged with a negative charge by friction with the conductivematerial of the second charging part 140. In addition, the firstcharging part 110 may include an organic polymer such as poly(methylmethacrylate) PMMA, polyethylene terephthalate (PET),polyetheretherketone (PEEK), cycloolefin copolymer (COC), orpolytetrafluoroethylene (PTFE). The first charging part 110 may includean inorganic polymer such as polydimethylsiloxane (PDMS) or organicallymodified ceramic (ORMOCER). The above-listed materials are examples, andinventive concepts are not limited thereto.

In another example, the surface S2 of the first charging part 110 may becharged with a positive charge by friction with the second charging part140, and the surface of the second charging part 140 may be charged witha negative charge by friction with the first charging part 110. Thesecond charging part 140 may include a conductive material for easyelectric connection with the grounding unit 130. The conductive materialmay include at least one of aluminum (Al), copper (Cu), gold (Au), andsteel that are easily charged by friction. The first charging part 110may include at least one of polyformaldehyde, ethylcellulose, polyamide,melamine formol, wool, silk, mica, and nylon that are easily chargedwith a positive charge by friction with the conductive material. Theabove-listed materials are examples, and inventive concepts are notlimited thereto.

At least one of the first and second charging parts 110 and 140 may bedoped with a p-type dopant or an n-type dopant so as to adjust chargingcharacteristics of the surface thereof. Examples of a source of thep-type dopant may include ionic liquids such as NO₂BF₄, NOBF₄, orNO₂SbF₆; acidic compounds such as HCl, H₂PO₄, CH₃COOH, H₂SO₄, or HNO₃;and organic compounds such as dichlorodicyanoquinone (DDQ), oxone,dimyristoylphosphatidylinositol (DMPI), or trifluoromethanesulfoneimide.Other examples of the source of the p-type dopant may include HPtCl₄,AuCl₃, HAuCl₄, AgOTf (silver trifluoromethanesulfonate), AgNO₃, H₂PdCl₆,Pd(OAc)₂, and Cu(CN)₂.

Examples of a source of the n-type dopant may include a reductionproduct of a substituted or unsubstituted nicotinamide; a reductionproduct of a compound which is chemically bound to a substituted orunsubstituted nicotinamide; and a compound including at least twopyridinium moieties in which a nitrogen atom of at least one of thepyridinium moieties is reduced. For example, the source of the n-typedopant may include nicotinamide mononucleotide-H (NMNH), nicotinamideadenine dinucleotide-H (NADH), nicotinamide adenine dinucleotidephosphate-H (NADPH), or viologen. Alternatively, the source of then-type dopant may include a polymer such as polyethyleneimine (PEI).Alternatively, the n-type dopant may include an alkali metal such aspotassium (K) or lithium (Li). The above-listed p-type dopant materialsand n-type dopant materials are examples. That is, any other materialsmay be used as the p-type dopant and the n-type dopant.

The grounding unit 130 may be electrically connected to the chargereservoir 133. The charge reservoir 133 may include ground or aconductive member having substantially no variation in electricpotential. When the second charging part 140 contacts the grounding unit130, the charge reservoir 133 and the second charging part 140 may beelectrically connected to each other through the grounding unit 130. Ifthe second charging part 140 is connected to the charge reservoir 133through the grounding unit 130, the electric potential of the secondcharging part 140 may become substantially equal to the electricpotential of the charge reservoir 133.

The first and second electrodes 122 and 124 may be spaced apart fromeach other in a direction in which the second charging part 140 slides.The first and second electrodes 122 and 124 may include a materialhaving a high degree of electric conductivity. For example, the firstand second electrodes 122 and 124 may include at least one of graphene,carbon nanotube (CNT), indium tin oxide (ITO), a metal, and a conductivepolymer. For example, the metal may include at least one of silver (Ag),aluminum (Al), copper (Cu), gold (Au), nickel (Ni), chromium (Cr), andplatinum (Pt). However, the metal is not limited thereto. The first andsecond electrodes 122 and 124 may have a single-layer or multilayerstructure.

Electrostatic induction may occur between the first and secondelectrodes 122 and 124 as the second charging part 140 slides. That is,while the second charging part 140 slides, charge may flow between thefirst and second electrodes 122 and 124 by electrostatic induction. Thetriboelectric generator may harvest energy from flow of charge betweenthe first and second electrodes 122 and 124.

FIG. 3 illustrates a modification of the triboelectric generatorillustrated in FIGS. 1 and 2, according to some example embodiments. Inthe following description with reference to FIG. 3, the samedescriptions as those given above with reference to FIGS. 1 and 2 willnot be repeated.

Referring to FIG. 3, a plurality of protrusions may be formed on atleast one of contact surfaces between the first charging part 110 andthe second charging part 140. The protrusions may include nano-pyramids,nano-wires, nano-balls, nano-rods, or the like. Since the protrusionsare formed on at least one of the contact surfaces between the firstcharging part 110 and the second charging part 140, when the firstcharging part 110 and the second charging part 140 are brought intocontact with each other, the amount of charge induced on each of thecontact surface of the first charging part 110 and the contact surfaceof the second charging part 140 may be increased.

FIG. 4 illustrates a modification of the triboelectric generatorillustrated in FIGS. 1 and 2, according to some example embodiments.

Referring to FIG. 4, a charge reservoir may include a conductive member131. In FIG. 4, the conductive member 133 a has a plate shape. However,this is an example, and the conductive member 133 a is not limitedthereto. The charge reservoir may be a conductive member having a highdegree of capacity. If the charge reservoir is connected to the secondcharging part 140 through the grounding unit 130, the charge reservoirmay exchange charges with the second charging part 140. That is, thecharge reservoir may vary the electric potential of the second chargingpart 140 by exchanging charges with the second charging part 140. Forexample, the electric potential of the charge reservoir may besubstantially the same as the electric potential of ground.

Hereinafter, an energy harvesting process using the triboelectricgenerator illustrated in FIGS. 1 and 2 will be described.

FIG. 5 is a view illustrating a state in which the second charging part140 is moved relative to the first charging part 110 through a slidingmotion. In the following description, charges illustrated in thedrawings are examples. That is, there may be various flows of charge intriboelectric generators of various embodiments.

The first and second charging parts 110 and 140 are moved relative toeach other. That is, sliding of the second charging part 140 may occurby the movement of the second charging part 140, the first charging part110, or both the first and second charging parts 110 and 140. The firstand second electrodes 122 and 124 and the grounding unit 130 may bearranged on a first substrate 10. The grounding unit 130 may be disposedbetween the first and second electrodes 122 and 124. While the secondcharging part 140 moves relative to the first substrate 10, the secondcharging part 140 may sequentially make contact with surfaces of thefirst charging part 110, the grounding unit 130, and the secondelectrode 124.

When the second charging part 140 and the first charging part 110 makecontact with each other, the first and second charging parts 110 and 140may be charged with opposite polarities. Referring to the example shownin FIG. 5, electrons move from the surface of the second charging part140 to the surface of the first charging part 110 because of frictionbetween the second charging part 140 and the first charging part 110.Owing to the movement of electrons, the second charging part 140 may becharged with a positive charge, and the first charging part 110 may becharged with a negative charge. However, this is merely an example. Thatis, the opposite case may also be possible. For example, electrons maymove from the surface of the first charging part 110 to the surface ofthe second charging part 140, and thus the first charging part 110 maybe charged with a positive charge and the second charging part 140 maybe charged with a negative charge.

FIG. 6 is a view illustrating a state in which the second charging part140 meets the grounding unit 130 as a result of a sliding motion.

Referring to FIG. 6, the second charging part 140 may be brought intocontact with an upper surface of the grounding unit 130 through asliding motion. Since a portion of the upper surface of the firstcharging part 110 is not in contact with the second charging part 140,electrostatic induction may occur between the first and secondelectrodes 122 and 124. Electrons may move from the first electrode 122to the second electrode 124 because of the electrostatic induction.While current flows between the first and second electrodes 122 and 124,electric energy may be harvested using a load 30 between the first andsecond electrodes 122 and 124.

The distance d1 between the first charging part 110 and the groundingunit 130 may be less than the width W of the second charging part 140.Here, the width W of the second charging part 140 refers to a length ofthe second charging part 140 in the sliding direction of the secondcharging part 140. Since the width W of the second charging part 140 isgreater than the distance d1 between the first electrode 122 and thegrounding unit 130, the second charging part 140 may contact both thefirst charging part 110 and the grounding unit 130 at the same time.Therefore, while current flows between the first and second electrodes122 and 124 by electrostatic induction, electrons may be supplied to thesecond charging part 140 through the grounding unit 130, and thus theelectric potential of the second charging part 140 may vary. In thiscase, since external electrons are introduced into the second chargingpart 140, electrostatic induction between the first and secondelectrodes 122 and 124 may be amplified. However, inventive concepts arenot limited thereto. For example, the distance d1 between the firstcharging part 110 and the grounding unit 130 may be greater than thewidth W of the second charging part 140. In this case, the secondcharging part 140 may make contact with the grounding unit 130 afterseparating from the first charging part 110.

If the second charging part 140 is brought into contact with thegrounding unit 130, the second charging part 140 may be electricallyconnected to the charge reservoir 133. The second charging part 140 mayinclude a conductive material for easy electric connection. If thesecond charging part 140 is brought into contact with the grounding unit130, the second charging part 140 and the charge reservoir 133 mayexchange charges with each other. Owing to this exchange of charges, theelectric potential of the second charging part 140 may become equal tothe electric potential of the charge reservoir 133. For example, if theelectric potential of the charge reservoir 133 is equal to the electricpotential of the ground, the charge reservoir 133 may supply electronsto the second charging part 140 through the grounding unit 130.

FIG. 7 is a view illustrating a state in which the second charging part140 is further moved relative to the first substrate 10 through asliding motion.

Referring to FIG. 7, the contact area between the second charging part140 and the first charging part 110 may gradually decrease because ofsliding. As the contact area between the second charging part 140 andthe first charging part 110 decreases, electrostatic induction may occurbetween the first and second electrodes 122 and 124. Due to theelectrostatic induction, current may flow between the first and secondelectrodes 122 and 124. The electric potential of the second chargingpart 140 may be maintained to be close to the electric potential of theground.

FIG. 8 is a view illustrating a state in which the second charging part140 meets the second electrode 124 as a result of a sliding motion.

Referring to FIG. 8, the first and second charging parts 110 and 140 mayseparate from each other. In addition, the second charging part 140 maymake contact with the grounding unit 130 and the second electrode 124.To allow the second charging part 140 to contact both the grounding unit130 and the second electrode 124, the distance d2 between the groundingunit 130 and the second electrode 124 may be less than the width W ofthe second charging part 140.

When the second charging part 140 contacts the grounding unit 130 andthe second electrode 124, the electric potential of the second electrode124 may vary because of the charge reservoir 133. For example, as anegative charge of the second electrode 124 moves to the chargereservoir 133 through the second charging part 140 and the groundingunit 130, the electric potential of the second electrode 124 may becomesubstantially equal to the electric potential of the ground.

FIG. 9 is a view illustrating a state in which the second charging part140 is further moved relative to the first substrate 10 as a result ofsliding.

Referring to FIG. 9, as electrons move from the second electrode 124 tothe grounding unit 130, the electric potential of the second chargingpart 140 and the second electrode 124 may become substantially equal tothe electric potential of the ground.

FIG. 10 is a view illustrating a state in which the second charging part140 is separate from the second electrode 124 as a result of a slidingmotion.

Referring to FIG. 10, as the second charging part 140 is separated fromthe second electrode 124, a first cycle illustrated with reference toFIGS. 5 to 10 may terminate. After the first cycle terminates, the firstcharging part 110 may be maintained in a negatively charged state. Thefirst electrode 122 may have a relatively large amount of positivecharge compared to the amount of negative charge because of theinfluence of negative charge of the first charging part 110. Aftercharge equilibrium is established as illustrated in FIG. 10, there maybe substantially no movement of charge until the next cycle in which thesecond charging part 140 and the first charging part 110 meet eachother. In addition, since the next cycle starts after the secondcharging part 140 and the second electrode 124 have the electricpotential of the ground, a larger amount of electric energy may beobtained in the next cycle.

Hereinafter, an explanation will be given of a process of harvestingenergy in cycles after the first cycle described with reference to FIGS.5 to 10.

FIG. 11 is a view illustrating a state in which the second charging part140 approaches the first charging part 110.

Referring to FIG. 11, the first charging part 110 may already have anegative charge unlike the case described with reference to FIG. 5.

FIG. 12 is a view illustrating a state in which the second charging part140 contacts the first charging part 110 through a sliding motion.

Referring to FIG. 12, since the first charging part 110 is already in acharged state, the amount of electron exchange between the first andsecond charging parts 110 and 140 may be relatively small. The secondcharging part 140 may be affected by the negative charge distributed onthe surface of the first charging part 110. A positive charge may beinduced on a lower surface of the second charging part 140, and anegative charge may be induced on an upper surface of the secondcharging part 140.

FIG. 13 is a view illustrating a state in which the second charging part140 meets the grounding unit 130 as a result of a sliding motion.

When the second charging part 140 contacts the grounding unit 130, theelectric potential of the second charging part 140 may vary to theelectric potential of the ground. In this process, electrons may movefrom the second charging part 140 to the grounding unit 130.

FIG. 14 is a view illustrating a state in which the electric potentialof the second charging part 140 is varied by the flow of electronsillustrated in FIG. 13.

Referring to FIG. 14, a positive charge may remain in a portion of thesecond charging part 140 making contact with the first charging part110. The remaining positive charge of the second charging part 140 maybe balanced with the negative charge on the surface of the firstcharging part 110, and thus the electric potential of the secondcharging part 140 may become equal to the electric potential of theground. In addition, as electrons move from the second charging part 140to the grounding unit 130, the amount of positive charge may be greaterthan the amount of negative charge in the second charging part 140.

Since a portion of the upper surface of the first charging part 110 isnot in contact with the second charging part 140, electrostaticinduction may occur between the first and second electrodes 122 and 124.Due to the electrostatic induction, electrons may move from the secondelectrode 124 to the first electrode 122 for electrical equilibrium. Aselectrons flow between the first and second electrodes 122 and 124,electric energy may be harvested using the load 30 between the first andsecond electrodes 122 and 124.

FIG. 15 is a view illustrating a state in which the second charging part140 is further moved relative to the first substrate 10 as a result of asliding motion.

Referring to FIG. 15, as the contact area between the second chargingpart 140 and the first charging part 110 decreases, electrons may movefrom the first electrode 122 to the second electrode 124. In addition,electrons may move from the charge reservoir 133 to the second chargingpart 140, maintaining the electric potential of the second charging part140 to be equal to the electric potential of the ground. Since thesecond charging part 140 receives an external charge through thegrounding unit 130, the amount of energy harvest through the load 30 maybe amplified during sliding of the second charging part 140.

FIG. 16 is a view illustrating a state in which the second charging part140 is in contact with the second electrode 124 as a result of a slidingmotion.

Referring to FIG. 16, the first and second charging parts 110 and 140may separate from each other. In addition, the second charging part 140may make contact with the grounding unit 130 and the second electrode124. To allow the second charging part 140 to contact both the groundingunit 130 and the second electrode 124, the distance d2 between thegrounding unit 130 and the second electrode 124 may be less than thewidth W of the second charging part 140. The second electrode 124 may beconnected to the charge reservoir 133 through the second charging part140 and the grounding unit 130. As electrons move from the chargereservoir 133 to the second electrode 124, the electric potential of thesecond electrode 124 may become equal to the electric potential of thecharge reservoir 133. For example, the electric potential of the secondelectrode 124 may become substantially equal to the electric potentialof the ground.

FIG. 17 is a view illustrating a state in which the second charging part140 is separate from the second electrode 124 as a result of a slidingmotion in the state shown in FIG. 16.

Referring to FIG. 17, as the second charging part 140 separates from thesecond electrode 124, the cycle illustrated with reference to FIGS. 11to 16 may terminate. Referring to FIG. 17, after the processes describedwith reference to FIGS. 11 to 16, the first and second charging parts110 and 140 and the first and second electrodes 122 and 124 may have thesame charge distribution as that shown in FIG. 11. Therefore, if thesecond charging part 140 is slid again on the upper surface of the firstcharging part 110, the processes described with reference to FIGS. 11 to16 may be repeated. Thus, while the cycle is repeated, electric energymay be harvested from current flowing between the first and secondelectrodes 122 and 124. While the second charging part 140 is movedrelative to other members by a sliding motion, the grounding unit 130may exchange charges with the second charging part 140 and the secondelectrode 124. Since the second charging part 140 and the secondelectrode 124 exchange charges with the charge reservoir 133, which isan external device, the amount of electric energy harvest may beincreased during sliding cycles.

In FIG. 1, the first and second electrodes 122 and 124, the firstcharging part 110, and the grounding unit 130 are disposed on the firstsubstrate 10 having a flat shape. However, inventive concepts are notlimited thereto. For example, the first substrate 10 may have any othershape to easily repeat the cycles illustrated with reference to FIGS. 1to 17.

FIG. 18 is a perspective view illustrating a triboelectric generatorhaving a different shape, according to some example embodiments.

Referring to FIG. 18, the triboelectric generator may include a firstsubstrate 10 having a circular plate shape. A first electrode 122, agrounding unit 130, and a second electrode 124 may be arranged on thefirst substrate 10 in radial directions. In addition, a first chargingpart 110 may be placed on an upper surface of the first electrode 122.For example, the first electrode 122, the first charging part 110, thegrounding unit 130, and the second electrode 124 may have a fan shape.However, inventive concepts are not limited thereto.

A second charging part 140 may face an upper surface of the firstsubstrate 10 and may be rotatable relative to the first substrate 10.For example, the triboelectric generator may further include a secondsubstrate 12 on which the second charging part 140 is disposed. Thesecond substrate 12 may have a circular plate shape. When at least oneof the first and second substrates 10 and 12 is rotated, the secondcharging part 140 may slide on upper surfaces of the first charging part110, the grounding unit 130, and the second electrode 124. However,inventive concepts are not limited thereto. For example, thetriboelectric generator may not include the second substrate 12. Forexample, a rotation center of the second charging part 140 may beconnected to the first substrate 10 so that the second charging part 140may be slid on the upper surfaces of the first charging part 110, thegrounding unit 130, and the second electrode 124.

In FIG. 18, the first electrode 122, the grounding unit 130, and thesecond electrode 124 are arranged on the first substrate 10. However,inventive concepts are not limited thereto. For example, a plurality ofsets each including a first electrode 122, a grounding unit 130, and asecond electrode 124 may be disposed on the first substrate 10.Similarly, a plurality of second charging parts 140 may be disposed onthe second substrate 12.

FIG. 19 is a perspective view illustrating a triboelectric generatorhaving a different shape, according to some example embodiments.

Referring to FIG. 19, the triboelectric generator may include a firstsubstrate 10 and a second substrate 12 that have a circular plate shape.A first electrode 122 and a second electrode 124 may be arranged on thefirst substrate 10 in radial directions. In addition, a first chargingpart 110 may be placed on an upper surface of the first electrode 122.In addition, a grounding unit 130 may be placed on the second substrate12.

A rotation center of a second charging part 140 may be connected to thefirst and second substrates 10 and 12. The second charging part 140 maymove between the first and second substrates 10 and 12. While the secondcharging part 140 moves relative to the first and second substrates 10and 12, the second charging part 140 may sequentially slide on surfacesof the first charging part 110, the grounding unit 130, and the secondelectrode 124.

FIG. 20 is a perspective view illustrating a triboelectric generatorhaving a different shape, according to some example embodiments.

Referring to FIG. 20, the triboelectric generator may include a firstsubstrate 10 having a circular plate shape. A first electrode 122 and asecond electrode 124 may be arranged on the first substrate 10 in radialdirections. In addition, a first charging part 110 may be placed on anupper surface of the first electrode 122.

The triboelectric generator may include a ring having a conductivematerial portion 132 and an insulative material portion 134. Theconductive material portion 132 may be electrically connected to acharge reservoir 133 so as to function as a grounding unit. A secondcharging part 140 may slide on an inner circumferential surface of thering through a rotation motion relative to the ring. While the secondcharging part 140 slides on an inner circumferential surface of theinsulative material portion 134, the charge reservoir 133 and the secondcharging part 140 may not be electrically connected to each other. Whilethe second charging part 140 slides on an inner circumferential surfaceof the conductive material portion 132, the charge reservoir 133 and thesecond charging part 140 may be electrically connected to each other.The conductive material portion 132 may be located between the firstcharging part 110 and the second charging part 140.

FIG. 21 is a perspective view illustrating a triboelectric generatorhaving a different shape, according to some example embodiments.

Referring to FIG. 21, the triboelectric generator may include a firstsubstrate 10 having a circular plate shape. A first electrode 122 and asecond electrode 124 may be arranged on the first substrate 10 in radialdirections. In addition, a first charging part 110 may be placed on anupper surface of the first electrode 122.

The triboelectric generator may include a cylindrical case 40 having aconductive material portion 132 and an insulative material portion 134.The conductive material portion 132 may be electrically connected to acharge reservoir 133 so as to function as a grounding unit. A secondcharging part 140 may slide on an inner wall of the case 40 through arotation motion relative to the case 40. While the second charging part140 slides on an inner wall of the insulative material portion 134, thecharge reservoir 133 and the second charging part 140 may not beelectrically connected to each other. While the second charging part 140slides on an inner wall of the conductive material portion 132, thecharge reservoir 133 and the second charging part 140 may beelectrically connected to each other. The conductive material portion132 may be located between the first charging part 110 and the secondcharging part 140.

FIG. 22 is a cross-sectional view illustrating a triboelectric generatorhaving a different shape, according to some example embodiments.

Referring to FIG. 22, the triboelectric generator may include a thirdsubstrate 16 on which a first electrode 122, a grounding unit 130, and asecond electrode 124 are arranged. The third substrate 16 may have acircular post shape. Although the third substrate 16 is illustrated ashaving a circular post shape in FIG. 22, inventive concepts are notlimited thereto. For example, the third substrate 16 may have a hollowcylindrical shape. The first electrode 122, the grounding unit 130, andthe second electrode 124 may be disposed on an outer surface S4 of thethird substrate 16. The grounding unit 130 may be connected to a chargereservoir 133. In addition, a first charging part 110 may be disposed onan upper surface of the first electrode 122.

A second charging part 140 may move while facing the outer surface S4 ofthe first substrate 10. The triboelectric generator may further includea fourth substrate 18 on which the second charging part 140 is disposed.For example, the second charging part 140 may be disposed on an innersurface S5 of the fourth substrate 18. When at least one of the thirdand fourth substrates 16 and 18 is rotated, the second charging part 140may sequentially slide on upper surfaces of the first charging part 110,the grounding unit 130, and the second electrode 124. In this manner,the cycles described with reference to FIGS. 5 to 17 may be repeated.

In FIG. 22, the first electrode 122, the grounding unit 130, and thesecond electrode 124 are arranged on the third substrate 16. However,inventive concepts are not limited thereto. For example, a plurality ofsets each including a first electrode 122, a grounding unit 130, and asecond electrode 124 may be disposed on the outer surface S4 of thethird substrate 16. Similarly, a plurality of second charging parts 140may be disposed on the inner surface S5 of the second substrate 12.

In addition, unlike the structure shown in FIG. 22, the second chargingparts 140 may be disposed on the outer surface S4 of the third substrate16, and the first electrode 122, the first charging part 110, thegrounding unit 130, and the second electrode 124 may be disposed on theinner surface S5 of the fourth substrate 18.

FIG. 23 illustrates a triboelectric generator having a different shape,according to some example embodiments.

Referring to FIG. 23, a second charging part 240 may be slid on a firstcharging part 210 while being rotated relative to the first chargingpart 210. The second charging part 240 may slide on surfaces of thefirst charging part 210 and a second electrode 224 at a position betweenthe first charging part 210 and the second electrode 224. A firstelectrode 222 and the second electrode 224 may be spaced apart from eachother in a direction in which the second charging part 240 slides.

The first charging part 210 may be disposed on a lower surface of thefirst electrode 222 facing the second charging part 240. The secondcharging part 240 may face the first charging part 210 and mayintermittently contact the first charging part 210 through a slidingmotion. In addition, the second charging part 240 may intermittentlycontact the second electrode 224 through a sliding motion. A groundingunit 230 may include a conductive post. The grounding unit 230 may beelectrically connected to a charge reservoir 233, and when the secondcharging part 240 rotates, the grounding unit 230 may intermittentlycontact the second charging part 240. For example, the second chargingpart 240 may include protrusions 242 on outer surfaces thereof. When thesecond charging part 240 rotates, the protrusions 242 may intermittentlycontact the grounding unit 230.

Each of the first and second charging parts 210 and 240 and the firstand second electrodes 222 and 224 may include a plurality of radiallyextending wings. For example, the first and second charging parts 210and 240 and the first and second electrodes 222 and 224 may have a fanshape.

Hereinafter, operations of the triboelectric generator illustrated inFIG. 23 will be described. In the following drawings, only one of theplurality of wings of each of the first and second charging parts 210and 240 and the first and second electrodes 222 and 224 is illustratedfor ease of illustration.

FIG. 24 is a schematic cross-sectional view illustrating thetriboelectric generator according to some example embodiments.

Referring to FIG. 24, the second charging part 240 may be separate fromthe grounding unit 230, the second electrode 224, and the first chargingpart 210. The first charging part 210 may move in interlock with thefirst electrode 222. The first charging part 210 may approach the secondcharging part 240 as a result of a relative movement.

FIG. 25 is a view illustrating a state in which the first and secondcharging parts 210 and 240 are in contact with each other.

Referring to FIG. 25, the first and second charging parts 210 and 240may contact each other through a sliding motion. When the first andsecond charging parts 210 and 240 contact each other, surfaces of thefirst and second charging parts 210 and 240 may be charged withdifferent polarities. After the first and second charging parts 210 and240 contact each other, the first and second charging parts 210 and 240may move in interlock with each other. For example, the first and secondcharging parts 210 and 240 may move in interlock with each other likethe hour and minute hands of a clock.

FIG. 26 is a view illustrating a state in which the second charging part240 is in contact with the grounding unit 230.

Referring to FIG. 26, while the first and second charging parts 210 and240 move in interlock with each other, a protrusion 242 of the secondcharging part 240 may contact the grounding unit 230. When the secondcharging part 240 is electrically connected to the grounding unit 230,the electric potentials of the second charging part 240 and the chargereservoir 233 may become equal to each other. For example, the electricpotential of the second charging part 240 may become substantially equalto the electric potential of ground.

FIG. 27 is a view illustrating a state in which the second charging part240 is in contact with the second electrode 224.

Referring to FIG. 27, the second charging part 240 may contact thesecond electrode 224 through a sliding motion. When the second chargingpart 240 contacts the second electrode 224, the electric potential ofthe second electrode 224 may also become equal to the electric potentialof the ground.

FIGS. 28 and 29 are views illustrating the second charging part 240separating from the second electrode 224 and the first charging part210.

In the example shown in FIGS. 28 and 29, the second charging part 240first separates from the second electrode 224. However, inventiveconcepts are not limited thereto. For example, the second charging part240 may first separate from the first charging part 210 and may thenseparate from the second electrode 224. In another example, the secondcharging part 240 may separate from the first charging part 210 and thesecond electrode 224 substantially at the same time. Thereafter, asshown in FIG. 29, the second charging part 240 may separate from thegrounding unit 230.

If the second charging part 240 separates from the second electrode 224,the electric potential of the second electrode 224 may not be equal tothe electric potential of the ground. In addition, as the secondcharging part 240 separates from the first charging part 210, the firstand second electrodes 222 and 224 may have different electricpotentials. If the first and second electrodes 222 and 224 havedifferent electric potentials, current may flow between the first andsecond electrodes 222 and 224. While current flows between the first andsecond electrodes 222 and 224, electric energy may be harvested using aload 30 between the first and second electrodes 222 and 224. During theprocesses shown in FIGS. 24 to 29, the second charging part 240 and thesecond electrode 224 may exchange charges with the outside through thegrounding unit 230, and thus the amount of current flowing between thefirst and second electrodes 222 and 224 may be further amplified. Inaddition, as shown in FIG. 29, the first charging part 210, the secondcharging part 240, the second electrode 224, and the grounding unit 230are all separate from each other. From this state, the processesdescribed with reference to FIGS. 24 to 29 may be repeated.

FIG. 30 is a view illustrating a modification of the triboelectricgenerator shown in FIG. 23.

Referring to FIG. 30, a grounding unit may include conductive members232 and insulative members 234 alternately arranged in a direction inwhich a second charging part 240 rotates. The conductive members 232 maybe electrically connected to a charge reservoir 233, and when the secondcharging part 240 rotates, the conductive members 232 may intermittentlycontact the second charging part 240.

For example, the conductive members 232 and the insulative members 234may be disposed on an inner wall of a cylindrical case 50. Thedistribution of the conductive members 232 may be determined such thatthe conductive members 232 may contact the second charging part 240 inthe same regions as the regions in which the second charging part 240and the grounding unit 230 illustrated in FIGS. 26 to 28 contact eachother.

FIG. 31 is a cross-sectional view illustrating a triboelectric generatoraccording to some example embodiments.

Referring to FIG. 31, the triboelectric generator may include: a firstelectrode 322 and a second electrode 324 spaced apart from each other; afirst charging part 310 disposed on a lower surface of the firstelectrode 322; a second charging part 340 configured to slide in adirection (x-axis direction) while facing a lower surface of the firstcharging part 310, so as to be charged with a polarity opposite to thatof the first charging part 310 as a result of contact with the firstcharging part 310; and a grounding unit 330 configured to intermittentlyconnect the second charging part 340 to a charge reservoir 333 accordingto the movement of the second charging part 340.

The second charging part 340 may move relative to the first chargingpart 310 and the second electrode 324 at a position between the firstcharging part 310 and the second electrode 324. The second charging part340 may contact the lower surface of the first charging part 310 througha sliding motion. In addition, the second charging part 340 may bespaced apart from the second electrode 324. Therefore, while the secondcharging part 340 slides on the lower surface of the first charging part310, the second charging part 340 may not contact the second electrode324.

The second charging part 340 and the first charging part 310 may includematerials having different charging ratings. Therefore, when surfaces ofthe second charging part 340 and the first charging part 310 rubtogether, the first charging part 310 and the second charging part 340may be charged with different polarities.

For example, the first charging part 310 may be charged with a negativecharge by friction with the second charging part 340, and the secondcharging part 340 may be charged with a positive charge by friction withthe first charging part 310. The second charging part 340 may include aconductive material for easy electric connection with the grounding unit330. The conductive material may include at least one of aluminum (Al),copper (Cu), gold (Au), and steel that are easily charged by friction.In addition, the first charging part 310 may include at least one ofpolytetrafluoroethylene (Teflon), fluorinated ethylene propylene (FEP),poly(methyl methacrylate) (PMMA), polyvinylidene fluoride (PVDF),polycarbonate (PC), polyvinyl chloride (PVC), polyimide (Kapton),polypropylene (PP), polyethylene (PE), and polystyrene (PS) that areeasily charged with a negative charge by friction with the conductivematerial of the second charging part 340. In addition, the firstcharging part 310 may include an organic polymer such as poly(methylmethacrylate) PMMA, polyethylene terephthalate (PET),polyetheretherketone (PEEK), cycloolefin copolymer (COC), orpolytetrafluoroethylene (PTFE). The first charging part 310 may includean inorganic polymer such as polydimethylsiloxane (PDMS) or organicallymodified ceramic (ORMOCER). The above-listed materials are examples, andinventive concepts are not limited thereto.

In another example, the first charging part 310 may be charged with apositive charge by friction with the second charging part 340, and thesecond charging part 340 may be charged with a negative charge byfriction with the first charging part 310. The second charging part 340may include a conductive material for easy electric connection with thegrounding unit 330. The conductive material may include at least one ofaluminum (Al), copper (Cu), gold (Au), and steel that are easily chargedby friction. In addition, the first charging part 310 may include atleast one of polyformaldehyde, ethylcellulose, polyamide, melamineformol, wool, silk, mica, and nylon that are easily charged with apositive charge by friction with the conductive material. Theabove-listed materials are examples, and inventive concepts are notlimited thereto.

At least one of the first and second charging parts 310 and 340 may bedoped with a p-type dopant or an n-type dopant so as to adjust chargingcharacteristics of the surface thereof. Examples of a source of thep-type dopant may include ionic liquids such as NO₂BF₄, NOBF₄, orNO₂SbF₆; acidic compounds such as HCl, H₂PO₄, CH₃COOH, H₂SO₄, or HNO₃;and organic compounds such as dichlorodicyanoquinone (DDQ), oxone,dimyristoylphosphatidylinositol (DMPI), or trifluoromethanesulfoneimide.Other examples of the source of the p-type dopant may include HPtCl₄,AuCl₃, HAuCl₄, AgOTf (silver trifluoromethanesulfonate), AgNO₃, H₂PdCl₆,Pd(OAc)₂, and Cu(CN)₂.

Examples of a source of the n-type dopant may include a reductionproduct of a substituted or unsubstituted nicotinamide; a reductionproduct of a compound which is chemically bound to a substituted orunsubstituted nicotinamide; and a compound including at least twopyridinium moieties in which a nitrogen atom of at least one of thepyridinium moieties is reduced. For example, the source of the n-typedopant may include nicotinamide mononucleotide-H (NMNH), nicotinamideadenine dinucleotide-H (NADH), nicotinamide adenine dinucleotidephosphate-H (NADPH), or viologen. Alternatively, the source of then-type dopant may include a polymer such as polyethyleneimine (PEI).Alternatively, the n-type dopant may include an alkali metal such aspotassium (K) or lithium (Li). The above-listed p-type dopant materialsand n-type dopant materials are examples. That is, any other materialsmay be used as the p-type dopant and the n-type dopant.

The grounding unit 330 may be electrically connected to the chargereservoir 333. The charge reservoir 133 may include ground or aconductive member, the electric potential of which substantially doesnot vary, that is, maintains substantially a constant value. When thesecond charging part 340 contacts the grounding unit 330, the chargereservoir 333 and the second charging part 340 may be electricallyconnected to each other through the grounding unit 330. When the secondcharging part 340 is connected to the charge reservoir 333 through thegrounding unit 330, the electric potential of the second charging part340 may become substantially equal to the electric potential of thecharge reservoir 333.

The first and second electrodes 322 and 324 may include a materialhaving a high degree of electric conductivity. For example, the firstand second electrodes 322 and 324 may include at least one of graphene,carbon nanotube (CNT), indium tin oxide (ITO), a metal, and a conductivepolymer. For example, the metal may include at least one of silver (Ag),aluminum (Al), copper (Cu), gold (Au), nickel (Ni), chromium (Cr), andplatinum (Pt). However, the metal is not limited thereto. The first andsecond electrodes 322 and 324 may have a single-layer or multilayerstructure.

FIG. 32 is a view illustrating a modification of the triboelectricgenerator shown in FIG. 31. In the following description with referenceto FIG. 32, the same description as that given above with reference toFIG. 31 will not be repeated.

Referring to FIG. 32, a plurality of protrusions may be formed on atleast one of contact surfaces between the first charging part 310 andthe second charging part 340. The protrusions may include nano-pyramids,nano-wires, nano-balls, nano-rods, or the like. Since the protrusionsare formed on at least one of the contact surfaces between the firstcharging part 310 and the second charging part 340, when the firstcharging part 310 and the second charging part 340 are brought intocontact with each other, the amount of charge induced on each of thecontact surface of the first charging part 310 and the contact surfaceof the second charging part 340 may be increased.

FIG. 33 is a view illustrating a state in which the first and secondcharging parts 310 and 340 shown in FIG. 31 are in contact with eachother as a result of a sliding motion.

Referring to FIG. 33, when the first and second charging parts 310 and340 contact each other, the surfaces of the first and second chargingparts 310 and 340 may be charged with different polarities. In theexample shown in FIG. 33, the surface of the second charging part 340 ischarged with a positive charge, and the surface of the first chargingpart 310 is charged with a negative charge. However, inventive conceptsare not limited thereto. For example, the surface of the first chargingpart 310 may be charged with a positive charge, and the surface of thesecond charging part 340 may be charged with a negative charge.

FIG. 34 illustrates a state in which the second charging part 340 ismoved relative to the first charging part 310 through a sliding motion.

Referring to FIG. 34, a portion of the surface of the first chargingpart 310 may not be in contact with the second charging part 340.Electrons may move from the first electrode 322 to the second electrode324 because of electrostatic induction occurring in a region close tothe portion of the surface of the first charging part 310 that is not incontact with the second charging part 340. That is, current may flowbetween the first and second electrodes 322 and 324.

FIG. 35 is a view illustrating a state in which the second charging part340 is in contact with the grounding unit 330 as a result of a slidingmotion.

Referring to FIG. 35, the second charging part 340 may contact thegrounding unit 330 and may exchange charges with the charge reservoir333. Since the second charging part 340 exchanges charges with thecharge reservoir 333, the electric potential of the second charging part340 may become equal to the electric potential of the charge reservoir333. For example, electrons may move from the charge reservoir 333 tothe second charging part 340, and thus the electric potential of thesecond charging part 340 may become substantially equal to the electricpotential of the ground.

FIG. 36 is a view illustrating a state in which the second charging part340 approaches again the first charging part 310 after the cycledescribed with reference to FIGS. 31 to 34 is completed.

Referring to FIG. 36, in an electrical equilibrium after the cycledescribed with reference to FIGS. 31 to 35, the surface of the firstcharging part 310 may have a negative charge. In addition, the firstelectrode 322 may have a relatively large amount of positive charge, andthe second electrode 324 may have a relatively large amount of negativecharge.

FIG. 37 is a view illustrating a state in which the second charging part340 is in contact with the first charging part 310 as a result of asliding motion.

Referring to FIG. 37, since the first charging part 310 is already in acharged state, the amount of electron exchange between the first andsecond charging parts 310 and 340 may be relatively small. The secondcharging part 340 may be affected by the negative charge on the surfaceof the first charging part 310. A positive charge may be induced on anupper surface of the second charging part 340, and a negative charge maybe induced on a lower surface of the second charging part 340.

FIG. 38 is a view illustrating a state in which the second charging part340 is moved relative to the first charging part 310 through a slidingmotion.

Referring to FIG. 38, a portion of the surface of the first chargingpart 310 may not be in contact with the second charging part 340.Electrons may move from the first electrode 322 to the second electrode324 because of electrostatic induction occurring in a region close tothe portion of the surface of the first charging part 310 that is not incontact with the second charging part 340. As described with referenceto FIG. 36, since a new cycle is started after the electric potential ofthe second charging part 340 is varied by the charge reservoir 333,current flowing between the first and second electrodes 322 and 324 maybe increased. That is, the amount of current flowing between the firstand second electrodes 322 and 324 may be larger in the case of using thegrounding unit 330 than in the case of not using the grounding unit 330.

FIG. 39 is a view illustrating a state in which the second charging part340 is in contact with the grounding unit 330 as a result of a slidingmotion.

Referring to FIG. 39, the second charging part 340 may contact thegrounding unit 330 and may exchange charges with the charge reservoir333. Since the second charging part 340 exchanges charges with thecharge reservoir 333, the electric potential of the second charging part340 may become equal to the electric potential of the charge reservoir333. For example, electrons may move from the charge reservoir 333 tothe second charging part 340, and thus the electric potential of thesecond charging part 340 may become substantially equal to the electricpotential of the ground. As the electric potential of the secondcharging part 340 is equal to the electric potential of the ground, thefirst charging part 310 and the first and second electrodes 322 and 324may have the same state as that shown in FIG. 35. In addition, as thecycle described with reference to FIGS. 36 to 39 is repeated, electricenergy may be repeatedly harvested. In addition, since the secondcharging part 340 exchanges charges with the charge reservoir 333, theamount of electric energy harvest may be increased during slidingcycles.

FIG. 40 is a current-time graph of the triboelectric generatorillustrated in FIGS. 1 to 17, illustrating current flowing between thefirst and second electrodes 122 and 124, and current flowing in thegrounding unit 130. In FIG. 40, the right curve indicates currentflowing between the first and second electrodes 122 and 124, and theleft curve indicates current flowing in the grounding unit 130.

Referring to FIG. 40, the curve indicating current flowing between thefirst and second electrodes 122 and 124 may include two peaks (a) and(c) in different directions. The reason for this is that the directionof electron movement between the first and second electrodes 122 and 124shown in FIG. 14 is different from the direction of electron movementbetween the first and second electrodes 122 and 124 shown in FIG. 15. Inaddition, the curve indicating current flowing in the grounding unit 130may also have two peaks (b) and (d) in different directions. The reasonfor this is that the direction of electron movement in the groundingunit 130 shown in FIG. 14 is different from the direction of electronmovement in the grounding unit 130 shown in FIG. 15. Therefore, theoutput current flowing between the first and second electrodes 122 and124 of the triboelectric generator may be alternating current.

FIG. 41 is a graph for comparing an output current measured between thefirst and second electrodes 122 and 124 of the triboelectric generatordescribed with reference to FIGS. 1 to 17 with an output currentmeasured between the first and second electrodes 122 and 124 of thetriboelectric generator after the grounding unit 130 was removed fromthe triboelectric generator.

In FIG. 41, the left curve indicates an output current with respect totime in the case of not using the grounding unit 130, and the rightcurve indicates an output current with respect to time in the case ofusing the grounding unit 130.

FIG. 42 is a graph for comparing a voltage measured between the firstand second electrodes 122 and 124 of the triboelectric generatordescribed with reference to FIGS. 1 to 17 with a voltage measuredbetween the first and second electrodes 122 and 124 of the triboelectricgenerator after the grounding unit 130 was removed from thetriboelectric generator.

In FIG. 42, the left curve indicates a voltage between the first andsecond electrodes 122 and 124 with respect to time in the case of notusing the grounding unit 130, and the right curve indicates a voltagebetween the first and second electrodes 122 and 124 with respect to timein the case of using the grounding unit 130.

Referring to FIGS. 41 and 42, when the grounding unit 130 is not used,current flowing between the first and second electrodes 122 and 124 maybe lower than about 0.2 mA, and voltage between the first and secondelectrodes 122 and 124 may be merely about 50 V.

However, when the grounding unit 130 is used, current and voltagebetween the first and second electrodes 122 and 124 may be amplified.Since the charge reservoir 133 and the second charging parts 140exchange charges with each other through the grounding unit 130, currentand voltage between the first and second electrodes 122 and 124 may beamplified. When the grounding unit 130 is used, output current may beincreased by a factor of about 10, and a current peak of about 1 mA orgreater may be obtained. In addition, when the grounding unit 130 isused, output voltage may be increased by a factor of about 4, and avoltage peak of about 150V to about 200 V may be obtained.

FIG. 43 is a perspective view illustrating a triboelectric generatoraccording to some example embodiments. FIG. 44 is a side viewillustrating the triboelectric generator illustrated in FIG. 43, andFIG. 45 is a top view illustrating the triboelectric generatorillustrated in FIG. 43.

Referring to FIGS. 43 to 54, the triboelectric generator may include: afirst electrode 422 and a second electrode 424 spaced apart from eachother; a first charging part 410 disposed on an upper surface of thefirst electrode 422; a second charging part 440 configured to be chargedwith a polarity opposite to that of the first charging part 410 whenrubbed against the first charging part 410 through a sliding motion; anda first magnetic part 460. In addition, the triboelectric generator mayinclude a second magnetic part 470 interlocked with the second electrode424 so as to move the second electrode 424 relative to the secondcharging part 440 under the influence of magnetic force of the firstmagnetic part 460.

In addition, the triboelectric generator may include a grounding unit430 configured to intermittently connect a charge reservoir 433 to thesecond charging part 440 and the second electrode 424 to which thesecond magnetic part 470 is attached.

The first charging part 410, the first electrode 422, the grounding unit430, and the first magnetic part 460 may be interlocked with each other.Therefore, when the first charging part 410 rotates relative to thesecond charging part 440 and the second electrode 424, the firstelectrode 422, the grounding unit 430, and the first magnetic part 460may also rotate relative to the second charging part 440 and the secondelectrode 424.

Rotation of the second charging part 440 relative to the first chargingpart 410 may occur when the first charging part 410 or the secondcharging part 440 rotates. That is, rotation of the second charging part440 relative to the first charging part 410 may be accomplished byrotating the second charging part 440, or rotating the first chargingpart 410 in a state in which the second charging part 440 is fixed. Inaddition, rotation of the second charging part 440 relative to the firstcharging part 410 may be accomplished by rotating both the first andsecond charging parts 410 and 440.

For example, when the first charging part 410 rotates, the firstelectrode 422, the grounding unit 430, and the first magnetic part 460may also rotate in interlock with the first charging part 410. Tointerlock the first charging part 410, the first electrode 422, thegrounding unit 430, and the first magnetic part 460 with each other, thetriboelectric generator may include a first substrate 10 a on which thefirst electrode 422 and the first magnetic part 460 are disposed. Arotation shaft of the grounding unit 430 may be interlocked with thefirst substrate 10 a. When the first substrate 10 a rotates, the firstelectrode 422, the first charging part 410 disposed on the upper surfaceof the first electrode 422, the grounding unit 430, and the firstmagnetic part 460 may rotate together with the first substrate 10 a.

The first substrate 10 a may have a circular plate shape for ease ofrotation. The first electrode 422 and the first charging part 410 mayhave a fan shape. In FIG. 43, the first electrode 422 and the firstcharging part 410 are illustrated as having a semicircular plate shape.However, inventive concepts are not limited thereto. For example, thefirst electrode 422 and the first charging part 410 may have a fanshape, and the central angle of the fan shape may not be 180°. Inanother example, the first electrode 422 and the first charging part 410may having a radially extending shape other a fan shape. The secondcharging part 440 may also have a fan shape or a radially extendingshape.

In the example described above, the first charging part 410 rotatestogether with the first substrate 10 a. However, inventive concepts arenot limited thereto. For example, when the first charging part 410 doesnot rotate, the second charging part 440 and the second magnetic part470 may rotate relative to the first charging part 410. In this case,the first substrate 10 a may be omitted. The second magnetic part 470may rotate together with the second electrode 424 to which the secondmagnetic part 470 is attached. The second electrode 424 and the secondcharging part 440 may rotate in interlock with each other.

When the second charging part 440 rotates relative to the first chargingpart 410, surfaces of the first charging part 410 and the secondcharging part 440 may intermittently contact each other while slide oneach other. The second charging part 440 and the first charging part 410may include materials having different charging ratings. Therefore, ifthe surfaces of the second charging part 440 and the first charging part410 rub together, the surfaces of the second charging part 440 and thefirst charging part 410 may be charged with different polarities. Thetypes of charges of the first charging part 410 and the second chargingpart 440 are dependent on materials of the first charging part 410 andthe second charging part 440, for example, may be determined by relativepositions of the materials of the first charging part 410 and the secondcharging part 440 in a triboelectric series.

For example, the surface of the first charging part 410 may be chargedwith a negative charge by friction with the second charging part 440,and the surface of the second charging part 440 may be charged with apositive charge by friction with the first charging part 410. The secondcharging part 440 may include a conductive material for easy electricconnection with the grounding unit 430. The conductive material mayinclude at least one of aluminum (Al), copper (Cu), gold (Au), and steelthat are easily charged by friction. In addition, the first chargingpart 410 may include at least one of polytetrafluoroethylene (Teflon),fluorinated ethylene propylene (FEP), poly(methyl methacrylate) (PMMA),polyvinylidene fluoride (PVDF), polycarbonate (PC), polyvinyl chloride(PVC), polyimide (Kapton), polypropylene (PP), polyethylene (PE), andpolystyrene (PS) that are easily charged with a negative charge byfriction with the conductive material of the second charging part 440.The first charging part 410 may include an organic polymer such aspoly(methyl methacrylate) PMMA, polyethylene terephthalate (PET),polyetheretherketone (PEEK), cycloolefin copolymer (COC), orpolytetrafluoroethylene (PTFE). The first charging part 410 may includean inorganic polymer such as polydimethylsiloxane (PDMS) or organicallymodified ceramic (ORMOCER). The above-listed materials are examples, andinventive concepts are not limited thereto.

In another example, the surface of the first charging part 410 may becharged with a positive charge by friction with the second charging part440, and the surface of the second charging part 440 may be charged witha negative charge by friction with the first charging part 410. Thesecond charging part 440 may include a conductive material for easyelectric connection with the grounding unit 430. The conductive materialmay include at least one of aluminum (Al), copper (Cu), gold (Au), andsteel that are easily charged by friction. The first charging part 410may include at least one of polyformaldehyde, ethylcellulose, polyamide,melamine formol, wool, silk, mica, and nylon that are easily chargedwith a positive charge by friction with the conductive material. Theabove-listed materials are examples, and inventive concepts are notlimited thereto.

At least one of the first and second charging parts 410 and 440 may bedoped with a p-type dopant or an n-type dopant so as to adjust chargingcharacteristics of the surface thereof. Examples of a source of thep-type dopant may include ionic liquids such as NO₂BF₄, NOBF₄, orNO₂SbF₆; acidic compounds such as HCl, H₂PO₄, CH₃COOH, H₂SO₄, or HNO₃;and organic compounds such as dichlorodicyanoquinone (DDQ), oxone,dimyristoylphosphatidylinositol (DMPI), or trifluoromethanesulfoneimide.Other examples of the source of the p-type dopant may include HPtCl₄,AuCl₃, HAuCl₄, AgOTf (silver trifluoromethanesulfonate), AgNO₃, H₂PdCl₆,Pd(OAc)₂, and Cu(CN)₂.

Examples of a source of the n-type dopant may include a reductionproduct of a substituted or unsubstituted nicotinamide; a reductionproduct of a compound which is chemically bound to a substituted orunsubstituted nicotinamide; and a compound including at least twopyridinium moieties in which a nitrogen atom of at least one of thepyridinium moieties is reduced. For example, the source of the n-typedopant may include nicotinamide mononucleotide-H (NMNH), nicotinamideadenine dinucleotide-H (NADH), nicotinamide adenine dinucleotidephosphate-H (NADPH), or viologen. Alternatively, the source of then-type dopant may include a polymer such as polyethyleneimine (PEI).Alternatively, the n-type dopant may include an alkali metal such aspotassium (K) or lithium (Li). The above-listed p-type dopant materialsand n-type dopant materials are examples. That is, any other materialsmay be used as the p-type dopant and the n-type dopant.

The grounding unit 430 may be electrically connected to the chargereservoir 433. The grounding unit 430 may include a material such as ametal, a ceramic material, or a polymer. The charge reservoir 433 mayinclude ground or a conductive member having substantially no variationin electric potential. The grounding unit 430 may intermittently contactthe second charging part 440 while rotating relative to the secondcharging part 440. When the second charging part 440 contacts thegrounding unit 430, the charge reservoir 433 and the second chargingpart 440 may be electrically connected to each other through thegrounding unit 430. When the second charging part 440 is connected tothe charge reservoir 433 through the grounding unit 430, the electricpotential of the second charging part 440 may become substantially equalto the electric potential of the charge reservoir 433.

The first and second electrodes 422 and 424 may include a materialhaving a high degree of electric conductivity. For example, the firstand second electrodes 422 and 424 may include at least one of graphene,carbon nanotube (CNT), indium tin oxide (ITO), a metal, and a conductivepolymer. For example, the metal may include at least one of silver (Ag),aluminum (Al), copper (Cu), gold (Au), nickel (Ni), chromium (Cr), andplatinum (Pt). However, the metal is not limited thereto. The first andsecond electrodes 422 and 424 may have a single-layer or multilayerstructure.

As the second charging part 440 slides on the surface of the firstcharging part 410, electrostatic induction may occur between the firstand second electrodes 422 and 424. For example, while the contact areabetween the second charging part 440 and the first charging part 410varies, a movement of charge may be caused by electrostatic inductionbetween the first and second electrodes 422 and 424. Owing to theelectrostatic induction, the triboelectric generator may harvest energyfrom flow of charge between the first and second electrodes 422 and 424.

While the second charging part 440 rotates relative to the firstcharging part 410, the second magnetic part 470 may rotate relative tothe first magnetic part 460. While the second magnetic part 470 rotatesrelative to the first magnetic part 460, the distance between the firstand second magnetic parts 460 and 470 may vary. For example, the firstmagnetic part 460 may be attached to a lower surface of the firstsubstrate 10 a, and the second magnetic part 470 may be attached to anupper surface of the second electrode 424. However, inventive conceptsare not limited thereto.

As the distance between the first and second magnetic parts 460 and 470varies, the magnitude of magnetic force between the first and secondmagnetic parts 460 and 470 may vary. The second electrode 424 and thesecond charging part 440 may contact each other or separate from eachother according to the magnitude of magnetic force between the first andsecond magnetic parts 460 and 470.

In FIGS. 43 to 45, when the distance between the first and secondmagnetic parts 460 and 470 is relatively small, the second electrode 424and the second charging part 440 are spaced apart from each other. Inthis case, the first and second magnetic parts 460 and 470 may repulseeach other because mutually-facing surfaces of the first and secondmagnetic parts 460 and 470 have the same polarity. The second electrode424 may be spaced apart from the second charging part 440 by repulsiveforce between the first and second magnetic parts 460 and 470.

However, inventive concepts are not limited thereto. For example, thefirst and second magnetic parts 460 and 470 may attract each otherbecause the mutually-facing surfaces of the first and second magneticparts 460 and 470 have different polarities. In this case, when thefirst and second magnetic parts 460 and 470 approaches each other, thesecond electrode 424 and the second charging part 440 may contact eachother because of attractive force between the first and second magneticparts 460 and 470. Then, when the first and second magnetic parts 460and 470 move away from each other, the second electrode 424 may bespaced apart from the second charging part 440. For example, an elasticmember may be disposed between the second electrode 424 and the secondcharging part 440. When the first and second magnetic parts 460 and 470move away from each other, the second electrode 424 may be spaced apartfrom the second charging part 440 because of elastic force acting by theelastic member.

Hereinafter, an explanation will be given of how the triboelectricgenerator described with reference to FIGS. 43 to 45 harvests energy. Inthe following description, charges illustrated in the drawings areexamples. That is, there may be various flows of charge in triboelectricgenerators of various embodiments.

FIG. 46 is a view illustrating a state in which the first and secondcharging parts 410 and 440 contact each other through a sliding motion.FIG. 47 is a side view illustrating the triboelectric generatorillustrated in FIG. 46, and FIG. 48 is a top view illustrating thetriboelectric generator illustrated in FIG. 46.

Referring to FIGS. 46 to 48, the first charging part 410 may moverelative to the second charging part 440, and thus the surfaces of thefirst and second charging parts 410 and 440 may contact each other. Whenthe second charging part 440 slides on the surface of the first chargingpart 410, tribocharging may occur. For example, when the first andsecond charging parts 410 and 440 make contact with each other, thesurfaces of the first and second charging parts 410 and 440 may becharged with opposite polarities.

Referring to the example shown in FIG. 47, electrons move from thesurface of the second charging part 440 to the surface of the firstcharging part 410 because of friction between the second charging part440 and the first charging part 410. Owing to the movement of electrons,the second charging part 440 may be charged with a positive charge, andthe first charging part 410 may be charged with a negative charge.However, this is merely an example. That is, the opposite case may alsobe possible. For example, electrons may move from the surface of thefirst charging part 410 to the surface of the second charging part 440,and thus the first charging part 410 may be charged with a positivecharge and the second charging part 440 may be charged with a negativecharge.

Referring to FIG. 48, the first and second magnetic parts 460 and 470may be spaced further apart than shown in FIG. 45. Referring to FIG. 47,as the distance between the first and second magnetic parts 460 and 470increases, the distance d1 between the second electrode 424 and thesecond charging part 440 may become less than shown in FIG. 44.

FIG. 49 is a view illustrating a state in which the first charging part410 is further rotated relative to the second charging part 440. FIG. 50is a side view illustrating the triboelectric generator illustrated inFIG. 49, and FIG. 51 is a top view illustrating the triboelectricgenerator illustrated in FIG. 49.

Referring to FIGS. 49 to 51, as the first charging part 410 rotatesrelative to the second charging part 440, the contact area between thefirst and second charging parts 410 and 440 may increase. The groundingunit 430 may rotate together with the first charging part 410 and maycontact the second charging part 440. An end portion of the groundingunit 430 may contact an edge of the second charging part 440. When thegrounding unit 430 contacts the second charging part 440, the secondcharging part 440 and the charge reservoir 433 may be electricallyconnected to each other. The second charging part 440 may exchangecharges with the charge reservoir 433. For example, the second chargingpart 440 may receive electrons from the charge reservoir 433. If thesecond charging part 440 receives electrons from the charge reservoir433, the electric potential of the second charging part 440 may becomesubstantially equal to the electric potential of the ground.

When the electric potential of the second charging part 440 varies aselectrons are supplied to the second charging part 440, electrostaticinduction may occur between the first and second electrodes 422 and 424.For example, electrons may move from the first electrode 422 to thesecond electrode 424. That is, current may flow between the first andsecond electrodes 422 and 424. When current flows between the first andsecond electrodes 422 and 424, electric energy may be harvested from aload 30 a connected between the first and second electrodes 422 and 424.Owing to the electrostatic induction, the first electrode 422 may have arelatively large amount of positive charge, and the second electrode 424may have a relatively large amount of negative charge. Since the secondcharging part 440 exchanges charges with the charge reservoir 433through the grounding unit 430, current flowing between the first andsecond electrodes 422 and 424 may be amplified.

Referring to FIG. 51, the first and second magnetic parts 460 and 470may be spaced further apart than shown in FIG. 48. As the distancebetween the first and second magnetic parts 460 and 470 increases, themagnitude of magnetic force between the first and second magnetic parts460 and 470 may decrease. Referring to FIG. 50, as the magnitude ofmagnetic force between the first and second magnetic parts 460 and 470decreases, the distance d1 between the second electrode 424 and thesecond charging part 440 may decrease.

FIG. 52 is a view illustrating a state in which the first charging part410 is further rotated relative to the second charging part 440. FIG. 53is a side view illustrating the triboelectric generator illustrated inFIG. 52, and FIG. 54 is a top view illustrating the triboelectricgenerator illustrated in FIG. 52.

Referring to FIGS. 52 to 54, as the first charging part 410 rotatesrelative to the second charging part 440, the contact area between thefirst and second charging parts 410 and 440 may be maximized. As thecontact area between the first and second charging parts 410 and 440increases, a large amount of negative charge may be induced on thesurface of the first charging part 410. While the first charging part410 rotates relative to the second charging part 440, the end portion ofthe grounding unit 430 may slide on the edge of the second charging part440. As electrons move from the charge reservoir 433 to the secondcharging part 440, the electric potential of the second charging part440 may become equal to the electric potential of the charge reservoir433.

As a larger amount of negative charge is induced on the surface of thefirst charging part 410, electrostatic induction may occur between thefirst and second electrodes 422 and 424. For example, electrons may movefrom the first electrode 422 to the second electrode 424. Therefore, inthe first electrode 422, the amount of positive charge may be greaterthan the amount of negative charge.

Referring to FIG. 54, the first and second magnetic parts 460 and 470may be spaced further apart than shown in FIG. 51. As the distancebetween the first and second magnetic parts 460 and 470 increases, themagnitude of magnetic force between the first and second magnetic parts460 and 470 may decrease. Referring to FIG. 52, as the magnitude ofmagnetic force between the first and second magnetic parts 460 and 470decreases, the second electrode 424 and the second charging part 440 maycontact each other.

If the second electrode 424 contacts the second charging part 440, thesecond electrode 424 may be electrically connected to the chargereservoir 433 through the second charging part 440 and the groundingunit 430. The second electrode 424 may exchange charges with the chargereservoir 433. The electric potential of the second electrode 424 maybecome equal to the electric potential of the charge reservoir 433. Forexample, the electric potential of the second electrode 424 may becomesubstantially equal to the electric potential of the ground.

Electrons may move from the first electrode 422 to the second electrode424 because of the electrostatic induction between the first and secondelectrodes 422 and 424. As many electrons as the number of electronsmoved from the first electrode 422 to the second electrode 424 may movefrom the second electrode 424 to the charge reservoir 433. Therefore,the second electrode 424 may be maintained in an electrically neutralstate. Since the second electrode 424 is maintained in an electricallyneutral state, the amount of current flowing between the first andsecond electrodes 422 and 424 may be amplified.

FIG. 55 is a view illustrating a state in which the first charging part410 is further rotated relative to the second charging part 440. FIG. 56is a side view illustrating the triboelectric generator illustrated inFIG. 55, and FIG. 57 is a top view illustrating the triboelectricgenerator illustrated in FIG. 55.

Referring to FIGS. 55 to 57, as the first charging part 410 rotatesrelative to the second charging part 440, the contact area between thefirst and second charging parts 410 and 440 may decrease. In addition,as shown in FIG. 57, since the distance between the first and secondmagnetic parts 460 and 470 decreases, the second electrode 424 and thesecond charging part 440 may be separated from each other. As shown inFIG. 57, the end portion of the grounding unit 430 may be at a positionjust before separation from the second charging part 440.

If the first charging part 410 rotates further in the state shown inFIGS. 55 to 57, the first charging part 410 may return to the initialposition shown in FIGS. 43 to 45. If the first charging part 410 returnsto the initial position, there may be no movement of charge because ofelectrical equilibrium.

After the cycle described with reference to FIGS. 46 to 57, the firstcharging part 410 may be maintained in a negatively charged state unlikethe state shown in FIGS. 43 to 45. If relative rotation between thefirst and second charging parts 410 and 440 is continued, the processesdescribed with reference to FIGS. 46 to 57 may be repeated in the statein which the first charging part 410 is negatively charged. While thecycle is repeated, current may flow between the first and secondelectrodes 422 and 424 owing to electrostatic induction. While thesecond charging part 440 intermittently contacts the charge reservoir433, the second charging part 440 may exchange charges with the chargereservoir 433. Since the second charging part 440 exchanges charges withthe charge reservoir 433, current flowing between the first and secondelectrodes 422 and 424 may be amplified.

FIG. 58 is a view illustrating a modification of the triboelectricgenerator shown in FIG. 44. In the following description with referenceto FIG. 58, the same descriptions as those given above with reference toFIGS. 43 and 57 will not be repeated.

Referring to FIG. 58, a plurality of protrusions may be formed on atleast one of a contact surface of a first charging part 410 and acontact surface of a second charging part 440. The protrusions mayinclude nano-pyramids, nano-wires, nano-balls, nano-rods, or the like.Since the protrusions are formed on at least one of the contact surfaceof the first charging part 410 and the contact surface of the secondcharging part 440, when the first charging part 410 and the secondcharging part 440 contact each other, the amount of charge induced oneach of the contact surface of the first charging part 410 and thecontact surface of the second charging part 440 may be increased.

FIG. 59 is a view illustrating a modification of the triboelectricgenerator shown in FIG. 44.

Referring to FIG. 59, a charge reservoir 433 a may include a conductivemember. In FIG. 59, the conductive member has a plate shape. However,this is an example, and the conductive member is not limited thereto.The charge reservoir 433 a may be a conductive member having a highdegree of capacity. When the charge reservoir 433 a is connected to asecond charging part 440 through a grounding unit 430, the chargereservoir 433 a may exchange charges with the second charging part 440.That is, as the charge reservoir 433 a exchanges charges with the secondcharging part 440, the electric potential of the second charging part440 may become equal to the electric potential of the charge reservoir433 a. For example, the electric potential of the charge reservoir 433 amay be substantially the same as the electric potential of ground.

FIG. 60 is a view illustrating a triboelectric system according to someexample embodiments.

Referring to FIG. 60, a triboelectric system 1000 may include aplurality of triboelectric generators 500. The triboelectric generators500 may be arranged in an array on a substrate and may be electricallyconnected to a common circuit. The substrate may be in polygonal shape,but inventive concepts are not limited thereto. The triboelectricgenerators 500 may be exposed to wind. As such, the triboelectric system1000 may be useful to place on structures where environmental wind mayrotate the triboelectric generator. For example, the triboelectricsystem 1000 may be useful on an external surface of a building and/or anexternal surface (e.g., the roof) of a vehicle, but inventive conceptsare not limited thereto. As a non-limiting example, the triboelectricgenerator 500 in FIG. 60 may include the triboelectric generatordiscussed with reference to FIG. 23, but inventive concepts are notlimited thereto. Any one of the triboelectric generators described abovewith reference to FIGS. 1 to 59 may be used as one of the triboelectricgenerators 500. Also, the triboelectric generators 500 in thetriboelectric system may all be the same, or some of the triboelectricgenerators 500 may be different other triboelectric generators 500 inthe triboelectric system 1000.

FIG. 61 is a view illustrating a triboelectric system according to someexample embodiments.

Referring to FIG. 61, a triboelectric system 2000 may include atriboelectric generator arranged (see e.g., triboelectric generatordescribed in FIG. 2) arranged over a piston container 150 and a trough T(or other reflecting mirror). The piston container 150 may be positionedbetween a side of the second charging structure 140 and the trough T(other reflecting mirror). The trough T (other reflecting mirror) mayreflect light L from the sun S (and/or other light source) to heat afluid F in the piston container 150. The light L may also increase atemperature of the piston container 150 and the piston container 150 maytransfer thermal energy to the fluid F. As the light energy L heats thefluid F in the piston container 150, part of the fluid may volatilizeand push the base B of the piston 145 upward to move the second chargingstructure 140 in a vertical direction; consequently, the second chargingstructure 140 may slide along the second electrode 124, grounding unit130, and first charging structure 122. When the fluid F cools down, thesecond charging structure 140 may lower back toward the piston container150. The base B may be configured to move with minimal friction up anddown in the piston container 150. In other words, as the fluid F heatsup and volatizes, the volume expansion of the fluid may push the piston145 upward and move the second charging structure 140 upward. Also, asthe temperature of the fluid F decreases, the volume of the fluid maydecrease as the fluid F changes from a gas to a liquid; thus, the piston145 may no longer push the second electrode 124 up and the secondelectrode 124 may lower towards the piston container 150.

Triboelectric generators according to some example embodiments have beendescribed with reference to FIGS. 1 to 59, and triboelectric systemsaccording to some example embodiments have been described with referenceto FIGS. 60-61. According to the one or more of the above embodiments,the first and second charging parts may contact each other and may becharged with different polarities. In addition, current may flow betweenthe first and second electrodes when the first and second charging partsmove relative to each other. Electric energy may be harvested fromcurrent flowing between the first and second electrodes. In addition,the electric potential of the second charging part or the secondelectrode may vary as the grounding unit intermittent contacts thesecond charging part or the second electrode, and thus the amount ofcurrent flowing between the first and second electrodes may beamplified.

Any one of the above-described triboelectric generators may be includedas an electricity supply unit in a device such as a smartwatch, acellular phone, a radio, a biosensor, a position sensor, a bodytemperature sensor, a blood pressure sensor, or another triboelectricsystem. In addition, any one of the above-described triboelectricgenerators may be included in a mobile device configured for attachmentto a body part that almost always moves, such as the hands or legs, soas to convert kinetic energy of the hands or legs into electric energy.In addition, any one of the above-described triboelectric generators maybe included a machine to convert vibrational energy into electricenergy. Furthermore, the triboelectric generators may be used togenerate electric energy using vibration caused by wind, pressure,sound, or fluid flow.

It should be understood that example embodiments described herein shouldbe considered in a descriptive sense only and not for purposes oflimitation. Descriptions of features or aspects within each embodimentshould typically be considered as available for other similar featuresor aspects in other embodiments.

While one or more embodiments have been described with reference to thefigures, it will be understood by those of ordinary skill in the artthat various changes in form and details may be made therein withoutdeparting from the spirit and scope as defined by the following claims.

1. A triboelectric generator comprising: a first electrode and a secondelectrode spaced apart from each other; a first charging part and asecond charging part, the first charging part being on the firstelectrode, the first charging part being configured to be charged afirst polarity due to contact with the second charging part, the secondcharging part being configured to slide on a surface of the firstcharging part, the second charging part being configured to be chargedwith a second polarity that is opposite to the first polarity throughcontact with the first charging part; and a grounding unit configured tointermittently connect the second charging part to a charge reservoiraccording to movement of the second charging part, wherein the secondcharging part is configured to slide on the first charging part whilerotating relative to the first charging part, and the first electrodeand the second electrode are spaced apart from each other in a directionperpendicular to a direction in which the second charging part isconfigured to slide.
 2. The triboelectric generator of claim 1, whereinthe first charging part is on a lower surface of the first electrodefacing the second charging part.
 3. The triboelectric generator of claim1, wherein the grounding unit is electrically connected to the chargereservoir, and the grounding unit includes a conductive post configuredto intermittently contact the second charging part when the secondcharging part rotates.
 4. The triboelectric generator of claim 1,wherein the grounding unit includes a conductive member and aninsulative member alternately arranged in a direction in which thesecond charging part rotates, and the conductive member is electricallyconnected to the charge reservoir and configured to intermittentlycontact the second charging part.
 5. The triboelectric generator ofclaim 1, wherein the first charging part, the second charging part, andthe second electrode have a fan shape.
 6. The triboelectric generator ofclaim 1, further comprising: a first magnetic part below the firstelectrode; and a second magnetic part above the second electrode.
 7. Thetriboelectric generator of claim 6, wherein the second electrode isconfigured to be moved relative to the second charging part by magneticforce between the first magnetic part and the second magnetic part. 8.The triboelectric generator of claim 6, wherein mutually-facing surfacesof the first magnetic part and the second magnetic part have a samepolarity.
 9. The triboelectric generator of claim 6, wherein the firstmagnetic part is interlocked with the first electrode and the firstcharging part.
 10. The triboelectric generator of claim 6, wherein alower surface of the second charging part is configured to contact anupper surface of the first charging part while the second charging partrotates relative to the first charging part.
 11. The triboelectricgenerator of claim 6, wherein the first electrode, the first chargingpart, the grounding unit, and the first magnetic part are configured tointerlock with each other and to rotate relative to the second chargingpart.
 12. The triboelectric generator of claim 6, wherein the secondelectrode and the second charging part are configured to contact eachother or separate from each other depending on a distance between thefirst magnetic part and the second magnetic part.
 13. The triboelectricgenerator of claim 6, wherein the second electrode interlocked with thesecond magnetic part is configured to contact an upper surface of thesecond charging part when the first charging part and the secondcharging part contact each other.
 14. The triboelectric generator ofclaim 6, wherein the charging part comprises a protrusion on outersurface thereof.
 15. The triboelectric generator of claim 1, wherein thecharge reservoir includes a ground or a conductive member.
 16. Thetriboelectric generator of claim 1, wherein the first charging part ison an upper surface of the first electrode, and the upper surface of thefirst electrode faces the second charging part.
 17. The triboelectricgenerator of claim 1, wherein one of the first charging part and thesecond charging part comprises a metallic material.
 18. Thetriboelectric generator of claim 17, wherein the metallic materialcomprises at least one of aluminum (Al), copper (Cu), gold (Au), andsteel.
 19. The triboelectric generator of claim 1, wherein one of thefirst charging part and the second charging part comprises at least oneof polytetrafluoroethylene (Teflon), fluorinated ethylene propylene(FEP), poly(methyl methacrylate) (PMMA), polyvinylidene fluoride (PVDF),polycarbonate (PC), polyvinyl chloride (PVC), polyimide (Kapton),polypropylene (PP), polyethylene (PE), and polystyrene (PS).
 20. Thetriboelectric generator of claim 19, wherein an other of the firstcharging part and the second charging part comprises at least one ofpolyformaldehyde, ethylcellulose, polyamide, melamine formol, wool,silk, mica, and nylon.